Enzyme polymorphism in Posidonia oceanica, a seagrass endemic to the mediterranean

Enzyme polymorphism was used to investigate genetic variability in Posidonia oceanica (L.) Delile from natural meadows around Nice (Alpes-Maritimes and Var) and among eight populations, sampled from the collection in the Port-Cros National Park, which had originated in different parts of the Mediterranean. Of the 30 enzyme systems studied only six were found useful in the isozyme studies (peroxidases, PER; glucose-phosphate isomerases, GPI; superoxide dismutases, SOD; malate dehydrogenases, MDH; catalases, CAT; glutamate dehydrogenases, GDH). The results showed that of these six only two enzymes showed enzyme polymorphism, indicating low levels of polymorphism, The small intrapopulation isozyme variability in P. oceanica meadows near Nice concurs with previous suggestions that reproduction is predominantly clonal, corresponding with previously observed infrequency of flowering in meadows. In the French meadows studied, one locus out of the eight was found to be polymorphic; this locus, moreover, showed an excess of heterozygotes. This same genetic structure found in all three meadows around Nice suggests that the greater part of these populations is not isolated, perhaps because of their practically continuous distribution along the Mediterranean coast, with dissemination by currents both of fruits and of rhizome fragments.